ORCID Profile
0000-0003-1654-8858
Current Organisations
São Paulo State University Rio Claro, CEA, UNESP, Brazil
,
Universiteit Utrecht
,
Federal University of Rio de Janeiro, UFRJ, Brazil
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Publisher: Wiley
Date: 12-2006
Publisher: Elsevier BV
Date: 12-2006
DOI: 10.1016/J.JCONHYD.2006.06.008
Abstract: One possible way of integrating subsurface flow and transport processes with (bio)geochemical reactions is to couple by means of an operator-splitting approach two completely separate codes, one for variably-saturated flow and solute transport and one for equilibrium and kinetic biogeochemical reactions. This paper evaluates the accuracy of the operator-splitting approach for multicomponent systems for typical soil environmental problems involving transient atmospheric boundary conditions (precipitation, evapotranspiration) and layered soil profiles. The recently developed HP1 code was used to solve the coupled transport and chemical equations. For steady-state flow conditions, the accuracy was found to be mainly a function of the adopted spatial discretization and to a lesser extent of the temporal discretization. For transient flow situations, the accuracy depended in a complex manner on grid discretization, time stepping and the main flow conditions (infiltration versus evaporation). Whereas a finer grid size reduced the numerical errors during steady-state flow or the main infiltration periods, the errors sometimes slightly increased (generally less than 50%) when a finer grid size was used during periods with a high evapotranspiration demand (leading to high pressure head gradients near the soil surface). This indicates that operator-splitting errors are most significant during periods with high evaporative boundary conditions. The operator-splitting errors could be decreased by constraining the time step using the performance index (the product of the grid Peclet and Courant numbers) during infiltration, or the maximum time step during evapotranspiration. Several test problems were used to provide guidance for optimal spatial and temporal discretization.
Publisher: Wiley
Date: 27-10-2021
DOI: 10.1002/SAJ2.20328
Abstract: The water retention curve (WRC) of arable soils from the southeastern United States at different levels of compaction (no compaction, and 10 and 20% increases in soil bulk density) was estimated using the van Genuchten–Mualem (VG) model. The VG water retention parameters of the noncompacted soils were obtained first by fitting measured soil hydraulic data. To construct the WRC of the compacted soils, gravimetric values of the permanent wilting point (θ gw , 1,500 kPa) and the residual (θ gr ) water content were assumed to remain unchanged with compaction. The VG parameter α and exponent η after compaction were estimated using two approaches. In Approach 1, α and η were estimated from saturation, the permanent wilting point, and the residual water content. In Approach 2, the value of η was assumed to remain unchanged with compaction, which allowed α to be estimated immediately from the VG equation. Approach 2 was found to give slightly better agreement with measured data than Approach 1. The effect of compaction on the saturated hydraulic conductivity ( K s ) was predicted using semitheoretical approaches and the VG‐WRC function. HYDRUS‐1D was further used to simulate vertical infiltration into a single‐layered soil profile to determine the impact of compaction on the infiltration characteristics of the soils used in our analyses. Results showed that a 10–20% increase in soil bulk density, due to compaction, reduced cumulative infiltration ( I c ) at time T = T final (steady‐state) by 55–82%, and the available water storage capacity by 3–49%, depending upon soil type.
Publisher: Informa UK Limited
Date: 04-05-2022
Publisher: Elsevier BV
Date: 09-2020
Publisher: Elsevier BV
Date: 2020
Publisher: Elsevier BV
Date: 03-2011
Publisher: American Geophysical Union (AGU)
Date: 11-2015
DOI: 10.1002/2015WR017703
Publisher: Wiley
Date: 15-12-1999
DOI: 10.1002/(SICI)1099-1085(19991215)13:17<2847::AID-HYP903>3.0.CO;2-M
Publisher: Elsevier BV
Date: 06-2008
Publisher: Wiley
Date: 05-2008
DOI: 10.2136/VZJ2007.0084
Publisher: Elsevier BV
Date: 12-1997
Publisher: Elsevier BV
Date: 03-2020
Publisher: CSIRO Publishing
Date: 04-04-2022
DOI: 10.1071/CP21676
Abstract: Context Salinity is a major cause of yield loss in wheat globally. Aims and Methods To investigate the potential of silicon to minimise the effect of salinity in wheat, experiments were conducted using outdoor pots subjected to seven salinity treatments. Silicon (as potassium silicate K2SiO3) was applied as both a priming agent and foliar spray. Selected response functions were used to quantify wheat response to salinity as affected by silicon application. Key results Concentration of chlorophyll a, chlorophyll b and carotenoid decreased by 4.2, 3.6 and 1.4 mg/g FW respectively with increasing salinity up to an electrical conductivity of 14 dS/m. Increasing salinity levels increased maximum variable chlorophyll fluorescence yield in a dark-adapted state and decreased the photochemical quenching coefficient, the nonphotochemical quenching coefficient, non-photochemical quenching, actual quantum yield of PSII electron transport in the light-adapted state, and the apparent photosynthetic electron transport rate. The maximal efficiency of PSII photochemistry in the dark-adapted state was not significantly influenced by salinity. The response functions showed that the salinity threshold value and the salinity at which a given trait was reduced by 50% (EC50) were 5.7 and 12.1 dS/m, respectively. Conclusions The combined treatment of silicon (priming × foliar spray) was found to be the most effective, increasing salinity threshold value and EC50 by 32 and 2% respectively. Implications These findings give insight into the effects of salinity on wheat and demonstrate the potential of silicon applications to promote crop health in saline environments.
Publisher: American Society of Agricultural and Biological Engineers
Date: 2021
Publisher: American Geophysical Union (AGU)
Date: 05-2022
DOI: 10.1029/2021WR031600
Abstract: In his seminal paper on the solution of the infiltration equation, Philip (1969), 0.1016/b978-1-4831-9936-8.50010-6 proposed a gravity time, t grav , to estimate practical convergence time and the time domain validity of his infinite time series expansion, TSE, for describing the transient state. The parameter t grav refers to a point in time where infiltration is dominated equally by capillarity and gravity as derived from the first two (dominant) terms of the TSE. Evidence suggests that applicability of the truncated two‐term equation of Philip has a time limit requiring higher‐order TSE terms to better describe the infiltration process for times exceeding that limit. Since the conceptual definition of t grav is valid regardless of the infiltration model used, we opted to reformulate t grav using the analytic implicit model proposed by Parlange et al. (1982), 0.1097/00010694-198206000-00001 valid for all times and related TSE. Our derived gravity times ensure a given accuracy of the approximations describing transient states, while also providing insight about the times needed to reach steady state. In addition to the roles of soil sorptivity ( S ) and the saturated ( K s ) and initial ( K i ) hydraulic conductivities, we explored the effects of a soil specific shape parameter β , involved in Parlange's model and related to the type of soil, on the behavior of t grav . We show that the reformulated t grav (notably where F ( β ) is a β ‐dependent function) is about three times larger than the classical t grav given by . The differences between the classical t grav,Philip and the reformulated t grav increase for fine‐textured soils, attributed to the time needed to attain steady‐state infiltration and thus i + infiltration for inferring soil hydraulic properties. Results show that the proposed t grav is a better indicator of time domain validity than t grav,Philip . For the attainment of steady‐state infiltration, the reformulated t grav is suitable for coarse‐textured soils. Still neither the reformulated t grav nor the classical t grav,Philip are suitable for fine‐textured soils for which t grav is too conservative and t grav,Philip too short. Using t grav will improve predictions of the soil hydraulic parameters (particularly K s ) from infiltration data compared to t grav,Philip .
Publisher: American Society of Civil Engineers (ASCE)
Date: 07-2019
Publisher: MDPI AG
Date: 30-05-2017
DOI: 10.3390/W9060385
Publisher: Wiley
Date: 11-11-2021
Publisher: Walter de Gruyter GmbH
Date: 28-03-2019
Abstract: Complete descriptions of the particle-size distribution (PSD) curve should provide more information about various soil properties as opposed to only the textural composition (sand, silt and clay (SSC) fractions). We evaluated the performance of 19 models describing PSD data of soils using a range of efficiency criteria. While different criteria produced different rankings of the models, six of the 19 models consistently performed the best. Mean errors of the six models were found to depend on the particle diameter, with larger error percentages occurring in the smaller size range. Neither SSC nor the geometric mean diameter and its standard deviation correlated significantly with the saturated hydraulic conductivity ( K fs ) however, the parameters of several PSD models showed significant correlation with K fs . Porosity, mean weight diameter of the aggregates, and bulk density also showed significant correlations with PSD model parameters. Results of this study are promising for developing more accurate pedotransfer functions.
Location: Brazil
No related grants have been discovered for Martinus van Genuchten.